1. Field of the Invention
The present invention relates to terminals for provision on ends of elongated electrical conductors such as insulated wires and, more particularly, to terminals which are crimped against such wires thereby avoiding the use of any bonding material.
Many kinds of conductor end terminals are available for use in providing terminal means for making mechanical and electrical connections of the corresponding electrical conductor, such as an insulated wire, where the connection between the conductor and terminal is made by crimping. Many of these terminals employ one or more metal barrels, or tube sections, into at least one of which the uninsulated end of such a conductor is placed. Thereafter, the tube is crimped against that uninsulated end. Such a crimp secures both an electrical connection and a mechanical connection between the terminal and the wire. As a result, use of solder or other bonding material between the terminal and the wire can be avoided to reduce time for assembly and the cost thereof. Often, serrations or protuberances directed from the tube section inner surface into the passageway are present to provide additional aid in securing a good mechanical connection.
There are competing considerations in choosing the metal to be used in forming such a terminal. A connecting portion for making contact with other objects usually can be of a relatively small gauge where used, as is typical, just for purposes of making contact with other terminals, other kinds of connectors or the like. However, the ability of the barrel, or tube section, to make a good crimp for providing an interconnection of substantial mechanical strength depends, to a significant degree, on the thickness (or gauge if a single sheet) of the metal used in forming the tube section wall.
Increasing the thickness of the tube section wall relative to the thickness of the connecting portion is expensive if two different gauges of metal are to be joined. This can be overcome by the use of a folded-over portion of a thinner gauge metal used for both the connecting portion and the tube section portion, such as is shown in U.S. Pat. No. 4,142,771 to Barnes et al. Shown there is a barrel or tube section constructed of two tabs of metal, each having serrations therein, and each of which is folded toward the other against the metal joining them to form the barrel of the terminal. Thus, a thicker tube section wall is obtained than could be obtained from just a single sheet of metal of the same thickness.
Another method for obtaining a thicker wall is to use a metal sleeve over a single sheet thick metal barrel, as shown in U.S. Pat. No. 3,594,713 to Thoman. This shows a serrated barrel with a sleeve thereover which provides a double wall barrel. The sleeve has an end portion folded over against itself to achieve a mechanical connection with the wire.
Another difficulty in maintaining a good mechanical connection is the tendency of a barrel with seams to spread apart at those seams when tension is placed between the terminal and the wire crimped thereon. This spreading of the seams tends to cause a loosening of the grip of the crimped portion at the terminal to the wire which can lead to a mechanical connection failure. The occurrence of more than one seam in the barrel, such as because a seam caused by folding portions of a sheet toward one another in making a double wall, tends to aggravate this problem. One means of providing a stronger seam is by the use of a locking tab such as is shown in U.S. Pat. Nos. 3,051,773 to Batcheller and 3,404,368 to Roberts et al.
Thus, an electrical terminal with a strong barrel or tube section wall and having no more than one seam would be desirable. Such a barrel would be further enhanced by means to prevent the seam from spreading during use.